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Scientific Papers of the Bureau of Standards

Scientific Papers of the Bureau of Standards

Washington, D.C.: National Bureau of Standards, 1919-1928.

Merged with: Technologic papers of the Bureau of Standards and Bureau of Standards Journal of Research


National Institute of Standards and Technology Research Library
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FEDLINK - United States Federal Collection
Scientific Papers of the Bureau of Standards
National Institute of Standards and Technology Research Library
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coblentz, w.w.
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clark, e.p.
grover, f.w.
hidnert, p., sweeney, w.t.
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This is a second part of a general investigation of etching reagents. The following materials were used: Copper alloys including brasses, bronze, and aluminum bronze; nickel; and the alloys of nickel, monel metal, cupro-nickel and nickel brass.
These measurements form a portion of the work undertaken by the Bureau of Standards in the determination of the thermal properties of materials used as refrigerating media. The existing data on the vapour-pressure-temperature relation for ammonia are undoubtedly sufficiently accurate to meet the requirements of refrigeration engineering. The Clapeyron equation, however, offers a means of correlating the measurements of the latent heat of vaporisation [see Abs. 1918A00278] with the data on...
Electron tube amplifiers may make use of either radio frequency amplification or audio frequency amplification, or both. Radio-frequency amplification consists in the amplification of the received radio-frequency current before it is detected. The use of radio-frequency amplification makes it possible to receive a very weak signal which cannot be heard at all if only audio frequency amplification is used. The coil antennas used in direction finding work receive only a very feeble signal, and...
Single-layer coils wound on formers so that each turn encloses a regular polygon are much used in radio measurements since such coils are easy to construct, have small self-capacity, and the wire is only supported by solid dielectric at the vertices of the polygon, thus reducing dielectric losses to a minimum. The paper provides formulae from which the inductance of coils wound on triangular, square, hexagonal or octagonal formers can be calculated. It is shown that the polygonal coil has an...
Describes an investigation of the permeability of rubber to a number of different gases. It is found that the permeability of rubber compounds varies with the composition. Ageing, or over-vulcanisation is accompanied by a decrease in permeability. Rubber which shows a very low permeability for these reasons is, however, usually very much deteriorated and frequently brittle. The permeability to any gas is found to be directly proportional to its partial pressure, provided the total pressure is...
Part 1 deals with the materials and construction of various spheres, and describes in detail the construction of a reinforced concrete sphere at the Bureau of Standards. It gives tests of the accuracy of integration by this sphere, the absorption of light by the sphere coating and by objects in the sphere, and the effect of the position of lamps. Proper methods of operation are also outlined. Part 2 gives a fairly complete resume of the general theory of the sphere, with the addition of a...
Describes the methods employed at the Bureau of Standards.
New formulae are developed for the resistance and inductance of parallel "go and return" circuits consisting of the same number, size, and spacing of wires as in the coil. The conditions are examined under which these formulae are applicable to the coils. The methods are an extension of that of Curtis [Abstract 1921A00306]. Experimental results are given at frequencies of 1000 to 3000 on large coils wound with bare copper wire 5.19 mm. diam. The measured values agree very closely with...
Expansion tests were made for various temperature ranges between room temperature and 750 degrees C. on molybdenum ingots prepared from fine and coarse-grained molybdenum powders and on samples swaged to various diameters. The results are presented in figures and tables. Series 1 to 4 (molybdenum samples swaged to various diameters). - Some of the expansion curves or. heating show marked changes in the rote of expansion at about 350 degrees C. In most cases the plotted observations on cooling...
In the present investigation the specific volume of saturated ammonia vapour was measured in the temperature interval - 50 degrees to 50 degrees C. by two methods - one involving a direct determination of the mass of the vapour contained in a known volume, and the other, an optical method, involving measurements of the index of refraction of the vapour. In the case of the first method the effect of adsorption was studied and found to be of a magnitude comparable with the limit of accuracy of...
Gives reproductions of photomicrographs to show the value of ammonium persulphate as a revealer of crystalline heterogeneity and chemical inhomogeneity in iron. Various features are revealed by this means which would be missed if other etching agents were employed.
A brief review of various methods which have been proposed for chemical analyses by means of the spectrum is followed by a detailed description of the principle, apparatus, and procedure employed in making quantitative analyses from the spectra of condensed sparks. The practical application of this method is illustrated by three examples taken from the work of the spectroscopy section of the Bureau of Standards and deals with the quantitative determination of impurities in various samples of...
The pressure gage- a number of quartz plates suitably cut are arranged condenser fashion in a stack and introduced in an electric circuit. The quartz plates are subjected to the gas pressure to be measured by means of a piston. The combination of these constitutes a gage which is screwed into the wall of the gas chamber and the leads are brought out through holes drilled through the wall. The rec ording galvanometer- a ballistic galvanometer whose period is long compared to the duration of the...
At sufficiently high frequencies difficulty is encountered in discussing the resistance of a coil owing to (1) the skin effect and (2) the capacity effect. The capacity effect is dealt with in the present paper, and it is believed that the modifications introduced in this treatment by the skin effect are only minor. The capacity effect results in the non-uniform distribution of current in the coil considered. It appears to be necessary to define the resistance of a coil not for the coil as a...
The author gives an elementary theory of the spherical aberration of thin lenses, using a notation which is due to Coddington where the aberration is expressed in terms of two factors, the shape and position factors. It is shown how to calculate quickly the aberration of any thin lens for any position of the object and to formulate a statement of the conditions under which the spherical aberrations of two thin lenses will compensate one another. The latter is confined to the simplest case when...
For several years the Bureau of Standards has been conducting tests and measurements of the characteristics of photographic light-sensitive materials. The ultimate object of the investigation is to standardize methods and the necessary conditions for testing these materials. At the present time workers in this field are using different standards, with the result that the data obtained are not directly comparable. It is hoped that this work will lead to the standardization that is so much needed.
The modulator tubes of radio-telephone transmitters used in commercial and military sets operate essentially as aperiodic power amplifiers of speech currents. The load on these tubes is determined approximately by the volt-ampere characteristics of the radio-generating circuit, as measured at its plate power-input terminals. At speech frequencies other effects occur as follows: (1) Current to the modulators and the generating circuit in parallel is supplied through an audio-frequency choke...
Striæ in optical glass may be divided into two classes; (i) those which appear as isolated bright streaks on a dark background, and (ii) those in which such bright streaks are very numerous and run into one another. This paper describes the investigation of a specimen of the former variety, containing a single approximately plane and very narrow stria - resembling a crack in the glass - which was ground and polished so that the stria was approximately perpendicular to the polished...
A more complete account of the work dealt with in Abs. 1920B00761.;
Topic: Index
The effective capacity of an inductance coil depends in general both on the capacities existing between parts of the coil itself and on the capacities existing between parts of the coil and the ground. On account of the importance of capacity effects in h.f. inductance coils, careful studies of these effects, both theoretical and experimental, have been made. An interesting result which has been found is that one effect seems to depend primarily on the capacity of the coil to earth. This effect...
The author first presents a summary of previous methods of measuring the absolute reflecting powers of surfaces. Nutting's apparatus depended on the principle of infinite parallel planes, and was subject to various inaccuracies. Most of the other devices utilise the integrating sphere. Apparatus. - The new reflectometer devised by the author utilises a sphere with whitened interior, a portion of which can be removed and the surface to be examined substituted. A narrow beam of light can be...
This paper gives data on the linear thermal expansion of 4 samples of aluminum and 51 samples of important aluminum alloys. The preparation, chemical composition, heat treatment, etc., are included. Most of the specimens were examined from room temperature to about 500 degrees Celsius. Typical expansion curves of the various groups of samples are shown and discussed.
The methods previously applied to the study of critical potentials in the metallic vapours have been, with some modifications, used for the elements P, I, S, N, O, and H. The results obtained are described at length and tabulated. Excepting the case of hydrogen, these elements all show a resonance and ionisation potential similar in relative magnitude to those observed in metallic vapours [see Abs. 1921A00297]. Except for I and S, the actual magnitudes of the potentials are larger than the...
A sound-detecting device, such as a magnetophone or electrostatic transmitter, and two coils whose mutual inductance can be varied by known amounts constitute a measuring instrument. The sound detector and one coil are connected to an indicating instrument, consisting of a vacuum-tube amplifier, a rectifier, and galvanometer. The e.m.f. generated in the detecting instrument is compared by substitution with the e.m.f. generated in coil when the other carries a known current. Since the sound...
Specific volumes of pure ammonia under the pressure corresponding to saturation have been determined from -78° to 100° C. The method employed is similar to one previously used by Dieterici, and consists essentially in observing, at various temperatures, the volumes of the liquid and vapour phases in equilibrium in a closed vessel. The total mass of ammonia is given by M = [v/?] [(V-v)/u'], where u and u' are the specific volumes of liquid and vapour respectively, V the total volume of the...
By the visibility of radiant energy is meant the ratio of luminosity to radiant power at the various wave-lengths in the spectrum. The American Bureau of Standards, in co-operation with the Nela Research Laboratories, has made a new determination of the visibility of radiant energy by the step-by-step method, an equality-of-brightness method with little or no hue difference in the two parts of the photometric field. Between 490 and 680 /b m/mu inclusive, measurements were made upon 52...
A series of iron-carbon alloys with carbon content varying from 0.018 to 1.60 per cent, was subjected to two kinds of heat treatment; one group was first hardened by quenching from temperatures above the critical range and then drawn back to successively higher temperatures; another set was annealed /b in vacuo./ After each heat treatment, magnetisation curves and hysteresis data were taken, and in most cases the magnetic property is graphed with the drawing temperature. The hardened alloys...
A method already described [Abs. 1920B00390] is improved to measure hysteresis values in strong fields, and the results obtained for H/sub c/ and B/sub r/ are comparable with those found by means of the Burrows and Fahy permeameters. Graphs of residual induction and coercive force are given for 0.85% carbon steel annealed and quenched, and for KS magnet steel for fields up to 2500 gauss.
Although this paper is entitled 'The Radio Direction-Finder,' it really only deals with the solenoidal-coil type of direction-finder developed by the Bureau of Standards. The chief features which distinguish it are: (1) the mounting of the direction-finder coil directly over the magnetic compass; (2) the provision, exterior to the magnetic compass card, of a correction scale for obtaining a corrected wireless bearing; (3) the use of a balanced method of coupling in the unidirectional antenna...
Describes the preparation of different alloys of aluminium with magnesium and zinc. All these alloys were found to tarnish in time, so that they could not be used for permanent mirrors. The best in this respect was the compound Al/sub 3/Mg/sub 4/, and for this alloy a reflectivity of 92% was obtained at 0.7 ?. The zinc alloy was found to have a minimum reflectivity at 0.9 ? and a similar minimum was found for pure zinc at 1 ?.
Aluminum and its alloys have been the subject of much investigation during recent years, in the course of which the principal features of the constitution of most of the binary alloy systems with aluminum have been determined.
The work described in this paper was undertaken for the purpose of satisfying an increasing demand for accurate data on the thermal expansion of molybdenum.
The research formed part of an investigation of problems of searchlight illumination. The detection of objects illuminated by a searchlight beam is largely a matter of contrast. A screen was illuminated to a known value so that its brightness was comparable with that of the path of a searchlight beam. Upon this screen was projected a rectangular beam, of variable horizontal width. The observer thus saw a rectangular strip of light upon a light background, and the length of the strip was varied...
This describes in detail the methods employed by the Bureau of Standards, to test the properties of insulating materials. The properties for which methods of measurement are given are phase difference, and dielectric constant at radio frequencies, voltage effects at radio frequencies, volume resistivity, surface resistivity, density, moisture absorption, tensile strength, transverse strength, hard ness, impact strength, permanent distortion, machining qualities, thermal expansivity, and effects...
Topic: Index